Teeth for drill cutters



F. L. SCOTT TEETH FOR DRILL CUTTERS Filed J uly 19, 1943 flogd L. Scott INVENTOR W ATTORNEY Patented Nov. 21.1944

raa'rn i on Dam. cu'r'rans Floyd L. Scott, Houston, Tex.' asslgnor to Hughes Tool Company, Houston, Tex a corporation of Delaware Application July 1'9, 194:, Serial No. 495,280

1 Claims.

This invention pertains to theformation of cutters for use on well drills employed in the drilling of deep wells for oil, gas, and the like.

In drilling bore holes in the harder earth formations by .the rotary method, rotary rock' drills fitted with roller cutters rotatably mounted thereon are employed. The drill is secured. to the lower end of a hollow shaft or drill stem rotated from the surface. These cutters roll upon the bottom of the hole with an approximately true rolling motion as the'drill stem is rotated and engage and disintegrate the material to be removed. The roller cutters are provided with teeth thereon which are forced to penetrate the bottom of the bore hole by weight from the drill stem, which weight is applied thereon by controls in the hands of the operator.

The cuttings from the bottom and sides of the well are washed away by flushlng fluid pumped down from the surface through the hollowrotating drill stem and are carried in suspension in said fluid to the surface. This fluid also cleans and cools the cutters and keeps them clear of accumulated cuttings.

' The form and disposition of the teeth upon the cutters have been found to be extremely iniportant. The cutting edges must have a preponderance of cutting crests extending transversely of the direction of rotation in order to obtain sufficient traction to assure continued rotation'of the cutter on its bearings. Teeth having cutting crests extending circumferentially of the cutter have very little traction and cannot be relied upon to assist materially in causing rotation. Cutters with circumferentially crested.

It is an object of the invention to provide reinforcing webs which connect adjacent teeth together at one of their ends. Said teeth are pref- -erably connected together at their ends in sets of two, as illustrated herein, but obviously the idea is capable of wider application.

It is also desired that the reinforcing web connecting adjacent teeth be of sturdy construction and formed with a cutting crest whichwili as- I cutters in the drilling operation. I am to presist in the disintegration of the well bottom and make it easier to prevent the formation of areas of uncut bottom between the tracks cut thereon by the rows of teeth on the different cutters.

Experience 'has shown that the teeth upon different cutters, as well asthe teeth upon the same cutter on different rounds of the well bottom, tend to track in imprints made on the formation on previous rounds of the drill. Between adjacent imprints in each row the rock teeth tend to grow up. Between the circular paths cut on bottom by the rows of teeth on the different cutters, small ridges or projections tend to form which connect the rock teeth on bottom formed by the tracking teeth in each row, to similar teeth in adjacent rows. Thus the rock teeth on bottom are not easily broken ofl. They are tied to other rock teeth by bonds of rock connecting adjacent rows of rock teeth together. This is particularly noticeable along the wall of the hole. The outer row of rock teeth on bottom is so firm- 1y bound to the wall that it is difficult to break'it away.

It is therefore an object to dispose the teeth upon the cutters so that they will form a pattern on the bottom of the hole which will serve to most effectively break up the formation. I desire to so arrange and form the cutter teeththat the rock teeth formed on bottom by the action of the cutters will be separate and disconnected from each other and from the wall of the hole and hence will be more easily broken off by the vent the formation of prominent rock teeth anywhere on bottom so that the bottom of the hole will be comparatively smooth.

In maklng'the connecting webs between adjacent teeth more effective in assisting in the cutting operation, as distinguished from reinforcing the regular teeth, it is an object to so arrange these webs that they will not always '60 well drill embodying the present invention.

Fig. 2 is a broken sectional detail illustrating the formation of the cutter teeth, this view being taken approximately an the line 2-2 of Fig. 1.

Fig. 8 is a sectional view througha well bore and showing about of the bottom thereof and indicating the imprints oftentimes formed on bottom by the old style of cutter tooth.

Fig. 4 is a similar quarter section of the well drill upon which the invention has been illus- 1 trated is one which has been in common use in the oil fields for many years. It comprises a head A having rotatably mounted on the lower end thereof a plurality of approximately conical shaped cutters, the small ends of the cones being pointed inwardly so that the cutters will have an approximately true rolling motion on bottom.

The cutters, as shown in Fig; l, have circumferential rows of cutting teeth I thereon, the rows of teeth on one cutter being offset to the rows of teeth on the two adjacent cutters, so that each row of teeth, except the outer row, will out a separate, track on bottom as the drill head is rotated. This oflsetting of the rows of teeth relative to each other also allows the teeth on one cutter to interflt between the rows of teeth on adjacent cutters, thus enabling each cutter'to be slightly larger than it otherwise could be made. As will be noted from Fig. 1 all three cutters are slightly different from each other. The No. I cone at the right has four rows of teeth offset from the three rows of teeth on the three rows on the No. III cutter at the top. The four rows on the No. II cutter has its teeth arranged to interflt with both No. I and No. III.

The present invention. consists in reinforcing the gage. It will be understood, of course, that prints are spaced apart and the material indicated at 1 between adjacent imprints is connected together by bonds of rock throughout the bottom. The cutter teeth by deepening the imprints on successive rounds will finally loosen the material and cause the intervening formation to crack oil into the form of chips which are carried away in the flushing fluid. Adjacent the wall of the hole where the formation between adjacent imprints 6 is bound to the wall of the hole by connecting the showing in both Figs. 3 and 4 is diagrammatic and also largely idealistic. The bottom is not formed in smooth imprints on bottom but the imprints are rough and irregular. The pattern is, however, approximately as is shown in these figures.

The diil'iculty caused by the use of teeth without the connecting webs is largely eliminated when the reinforcing webs are used and a different pattern on bottom is'formed. The webs adjacent teeth in the rows by connecting the adjacent elemental teeth' 2 together at one of their ends by a web of steel 3. Such a web reinforces the teeth at their ends and prevents:

them from breaking down and chipping off as they otherwise tend to do when forced into the hard rock which is being drilled. As illustrated in the drawing, the web 3 may join the outer end of the two adjacent teeth together in the row, or, as shown at to, the web may join together the inner ends ofthe two adjacent teeth in the row.,

It will be noted that the two teeth thus joined together form a cutting structure having a channel-shaped cross section. This structure we may call a cutting element. The web I which connects the two adjacent teeth widens at the base and is formed with a cutting crest so that it may assist in disintegrating material on bottom. This web therefore performs the function of strengthening the teeth and thus prolonging their life and also it has the function of helping to cut the formation on the bottom. of the well.

Toillustrate the manner in which teeth formed formed in connecting adjacent teeth in the manner described are arranged so that the connecting web on one round of the well bottom will form imprints of general rectangular U-shape. The cutting elements are arranged to reduce the tend ency to track in the same imprints on bottom by making the teeth of an uneven number. Thus on subsequent rounds of the cutter the web will tend to engage in a different place on bottom. The elemental teeth 2 tend to track in similar imprints formed inprior rotation to the cutter but the teeth joined by the connecting webs will tend not to engage in exactly the same track. This is assured by separating the pairs of teeth connected by the webs at some point on the circumference of the cutter by a tooth 2a, which is not reinforced. By making the number of teeth in the row uneven, we assure that cutter teeth will tend to creep relative to bottom approximately to the extent of one impression per revolution. The resulting pattern on bottom is shown in Fig. 4. The imprints formed by the cutter teeth 2. adjacent the gage are indicated by the numeral 8. The track cut by the outer web 3 will be seen at 9. The webs may be formed on the different cutters a't diiferentgends of the teeth. Thus in Fig. 1 the upper and left hand cutters have the teeth joined at the outer ends and the teeth of the righthand cutter are joined at their inner ends. 0n the inner rows it is desired that some In this view the side wall of the hole is shown a of the teeth be joined at their inner ends, as shown at to, and others joined at their outer ends, as shown at 3b. The webs at the adjacent ends of the different teeth will thus .cut on bottom circumferential rows 8, which tend to break up the formation betweenthe adjacent rock teeth It left on bottom by the adjacent tooth imprints 8. It will thus be seen that the rock teeth left on bottom by the imprints cut by the teeth and by the web will be disconnected on bottom from the rock teeth in adjacent rows. The rock teeth will thus stand up from bottom entirely separate from each other and be more easily broken-away by continued action of the cutter teeth as the drill advances. The rock teeth II will be seen to be entirely severed from the wall of the hole by the continuous outer groove or track cut by the webs 3 on the outer rows of teeth. The pattern on bottom is shown in Fig. 4, it being understood that this is very diagrammatic and at the bottom will not be smooth but will be broken up in somewhat irregular rock teeth,

said teeth being, however, separated from other rock teeth on bottom by circumferential tracks cut by the web joining adjacent teeth.

In Fig. 1 of the drawing some of the inner rows of teeth are shown as not connected by webs. n the teeth toward the inner portion of the cone the excessive wear which is undengone by the teeth adjacent the walls of the hol is not so severe and on some of the cutters the web may be omitted on the inner rows, particularly in the semi-hard formations. In some hard formations reinforcing webs may be employed on approximately all the rows. of teeth. The use of cutters of this character of reinforcing webs between the ends of adjacent teeth enable the cutters to last materially longer befor they become worn out.

Furthermore, they'assist in cutting theformation in such manner that the formation is more easily broken up and the cutters will drill more hole than is being drilled by the old type cutter and at a faster rate. It is believed that this is due largely to the manner in which the bottom is disintegrated. The hole will need less reaming because a full sized hole is maintained and as'the bottom is more efllciently disintegrated the actheir axes, said cutters having a plurality of circumferential rows of chisel-shaped teeth thereon 3. In a well drill cutter having it periphery longitudinally tapered and having a plurality of circumferentialiy arranged rows of chisel shaped cutter teeth, said rows being spaced apart thereon, with their cutting crests positioned approximately longitudinally of th cutter; the improvement consisting of teeth in a row arranged in sets, each set being connected together by a single reinforcing webextending between and connecting the adjacent corresponding ends of the teeth in the set, said webs being circumferentially disposed and spaced and having cutting crests thereon to assist in cutting the bottom of the hole.

4. In a cutter for well drills having circumferential rowsof chisel shaped teeth thereon spaced longitudinally of said cutter with the crests in planes approximately including the axis of rotation; the improvement consisting of connecting and reinforcing webs extending between the corresponding, adjacent ends of pairs of said teeth in a row, each of said pairs being connected by a single web and spaced from other similar pairs in the same row to allow circulation of flushing fluid between them, said webs having circumferentially extending cutting crests assisting in cutting thefull bottom of the hole, said rows being formed with an uneven number of cutting teeth in each row. j

5. In an approximately conical shaped cutter for well drills having spaced circular circumferential rows of approximately longitudinally crested teeth thereon; the combination of rein-v forcing webs extending between and connecting the adjacent corresponding ends of sets of said with the crests thereof extending lengthwise of the cutter and in planes radial to the cutter axis,

said rows being spaced apart and, the teeth on ferentially extending webs connecting pairs of wardly inclined positionand roll upon the well bottom, each cutter having a circumferential row of teeth thereon with cutting crests lengthwise adjacent teeth in a row together at one of their corresponding ends to form separate cutting units in the row separated from-the adjacent unit on either side in the same row by a space for passage of fluid, said webs acting to reinforce said teeth and also to assist'in cutting the bottom of the hole.

2. In a well drill having rolling cutter thereon,

said cutters having circular circumferential rows the tracks cut by said teeth.

a of the cutter acting to drill the bottom of the hole; the combination of webs, of the same height as the teeth, connecting sets of said teeth together to form cutting elements, each set having a single web extending between the a lacent corresponding ends of the teeth of the set and leaving spaces between adjacent sets of teeth for fluid circulation, and there being an uneven number of teeth in each row.

7. In a well drill cutter having a tapered cutting periphery and spaced circumferential rows of longitudinally extending cutting teeth thereon, the improvement including a reinforcing web extending between and connecting the corresponding ends of adjacent teeth in a row together, said webs being circumferentially disposed and spaced apart in the row and having cutting crests to cut circular tracks on the well bottom at the ends'oi' FLOYD L. SCOTT. 

